#include <iostream>
#include <string>
using namespace std;

class Student;

class Person{
protected:
  string _name;
  string _id;
  int _age;

public:
  static int _scount;

  Person()
  {
    ++_scount;
  }
  ~Person()
  {
    --_scount;
  }
};

int Person::_scount = 0;

class Student : public Person{
  string _stuid;
public:
};

class Teacher : public Person{
  string _jobid;
public:
};

void Test7(){
  cout << Person::_scount << endl;
  Student s1;
  Student s2;
  Student s3;
  cout << Person::_scount << endl;
  Teacher t1;
  Teacher t2;
  cout << Person::_scount << endl;
  cout << &Person::_scount << " " << &Student::_scount << " " << &Teacher::_scount << endl;
}

int main(){
  Test7();
  return 0;
}
